The subject matter herein relates generally to decoupling capacitors and, more specifically, to decoupling capacitors that may be used in high power systems, such as an RF system of an isotope production system.
Radioisotopes (also called radionuclides) have several applications in medical therapy, imaging, and research, as well as other applications that are not medically related. Systems that produce radioisotopes typically include a particle accelerator, such as a cyclotron, that accelerates a beam of charged particles (e.g., H− ions) and directs the beam into a target material to generate the isotopes. The cyclotron includes a particle source that provides the particles to a central region of an acceleration chamber. The cyclotron uses electrical and magnetic fields to accelerate and guide the particles along a predetermined orbit within the acceleration chamber. The magnetic fields are provided by electromagnets and a magnet yoke that surrounds the acceleration chamber. The electrical fields are generated by a pair of radio frequency (RF) electrodes (or dees) that are located within the acceleration chamber. The RF electrodes are electrically coupled to an RF power generator that may include, for example, oscillators, amplifiers, control circuitry, and power supplies. The RF power generator energizes the RF electrodes to provide the electrical field. The electrical field combines with the magnetic field within the acceleration chamber and causes the particles to take a spiral-like orbit that has an increasing radius. When the particles reach an outer portion of the orbit, the particles are directed toward the target material for radioisotope production. In addition to controlling the orbit of the particles, the RF electrodes may be used to pull the particles from a particle source in the acceleration chamber.
To operate the RF electrodes within the acceleration chamber, a considerable amount of electric power (e.g., 5 kW to 2 MW) is generated by the RF power generator and delivered to the RF electrodes. The power generator includes, among other things, a tube amplifier unit having a power electron vacuum tube. The vacuum tube may be, for example, a power triode having a cathode, anode, and control grid. The cathode is heated by a filament that receives current from a power supply. The heated filament causes the cathode to emit electrons, which flow through the vacuum tube toward the anode. The control grid is positioned between the cathode and anode and may be used to control the flow of the electrons.
The current for heating the filament is transmitted through one or more cables (or flying leads) and is capable of carrying a substantial amount of electromagnetic interference (EMI) from the power tube. To reduce the EMI, the power supply may be decoupled to ground. At least some known RF power generators use a plurality of conventional ceramic capacitors to decouple the power supply to ground. Although the ceramic capacitors may be effective in decoupling the power supply, the ceramic capacitors have certain drawbacks. For example, the ceramic capacitors may be brittle and are consequently at risk of being damaged during assembly and/or maintenance of the RF power generator. For instance, when the vacuum tube is replaced, the ceramic capacitors are detached from cable terminals and then re-attached to cable terminals using hardware and tools that can damage the ceramic capacitors. In addition to the above, the ceramic capacitors may be expensive and bulky, and it is often necessary to combine several ceramic capacitors together. Using multiple ceramic capacitors can be costly and occupy a substantial amount of space.